1. Field of the Invention
This invention relates to a disc drive apparatus used in an information processing apparatus, such as a personal computer.
2. Description of the Related Art
A hard disc drive apparatus or HDD (hereinafter referred to simply as a disc drive apparatus) is used in an information processing apparatus, such as a personal computer. The disc drive apparatus comprises a magnetic disc (hereinafter referred to simply as a disc) that is rotated by a spindle motor, a carriage that turns about a pivot, a positioning motor for driving the carriage, a box-shaped base, etc. The base contains therein the disc, carriage, positioning motor, etc.
The pivot is attached to the base. The carriage has a plurality of arms. Each arm is provided with a suspension. A magnetic head for writing data to and reading it from the disc is provided on the distal end portion of each suspension.
For example, a 2.5-inch disc drive apparatus has two discs for use as recording media. The carriage includes a top arm, a bottom arm, and a mid-arm. The mid-arm is disposed between the top and bottom arms. A suspension is attached to each of the arms. A slider that constitutes a magnetic head is mounted on the distal end portion of each suspension. One such disc drive apparatus is shown in FIG. 2 of Jpn. Pat. Appln. KOKAI Publication No. 2003-173643 or FIG. 3 of Jpn. Pat. Appln. KOKAI Publication No. 2004-95076, for example.
If a shock is applied to the disc drive apparatus, the arms swing as the base swings. In order to improve the operational shock characteristic performance of the disc drive apparatus, it is desirable to minimize the swings of the arms when the shock is applied. It is effective, in particular, to suppress the swings of the arms to cope with a short-duration shock that is applied for a short time (e.g., 0.4 sec or thereabouts).
FIG. 14 shows the frequency response characteristics of a conventional disc drive apparatus. In FIG. 14, a broken line represents the average of amplitudes of the base as a whole, a solid line represents the amplitude of a pivot position on the base (in which the pivot is mounted), and a dash-dotted line represents the amplitude of the top arm. A first bending mode of the top arm is at 1,263 Hz.
A solid line in FIG. 14 represents the fluctuation of the pivot position. In connection with the fluctuation of the pivot position, a low-frequency first vibration mode (Base 1st-1) is exhibited near 800 Hz. This low-frequency first vibration mode is a vibration mode in which the base is swung based mainly on the mass of the spindle motor (mass including the discs 13). Further, a high-frequency first vibration mode (Base 1st-2) is exhibited near 1,300 Hz. This high-frequency first vibration mode is a vibration mode in which the base is swung based mainly on the total mass of the spindle motor and the carriage.
In short, the pivot position of the conventional disc drive apparatus considerably fluctuates in at least two first vibration modes (Base 1st-1 and Base 1st-2). In particular, the pivot position fluctuates at frequencies near the first bending mode of the top arm. This fluctuation shakes the top arm and produces an amplitude (42 dB) that exceeds a permissible limit. Thus, the shock performance still requires improvement.